Solid compositions suitable for oral administration comprising L-carnitine and alkanoyl-L-carnitine magnesium tartrate

ABSTRACT

Stable and nonhygroscopic salts consisting of L-carnitine magnesium tartrate or lower alkanoyl-L-carnitine magnesium tartrate are disclosed that are suitable for preparing solid compositions useful as dietary or nutritional supplements for human use and as a fodder supplement for veterinary purposes.

The present invention relates to stable, non-hygroscopic, pharmacologically acceptable salts of L-carnitine and lower alkanoyl-L-carnitines which favourably lend themselves to the preparation of solid, orally administrable compositions. The present invention also relates to such compositions.

Various therapeutic uses of L-carnitine and alkanoyl derivatives thereof are already known. For instance, L-carnitine is used in the cardiovascular field for the treatment of acute and chronic myocardial ischaemia, angina pectoris, heart failure and cardiac arrhythmias.

In the nephrological field, L-carnitine is administered to chronic uraemics undergoing regular haemodialytic treatment to combat myasthenia and the onset of muscular cramps.

Other therapeutic uses relate to the normalization of the HDL:LDL+VLDL ratio and total parenteral nutrition.

It is also known that the salts of L(-)-carnitine and its alkanoyl derivatives present the same therapeutic or nutritional activities as those of the so-called inner salts and can, therefore, be used in their place, provided these salts are "pharmacologically acceptable", i.e. they do not present unwanted toxic or side effects.

In practice, then, the choice between an "inner salt" and a true L(-)-carnitine or alkanoyl-L(-)-carnitine salt will depend essentially on availability, economical and pharmacy considerations rather than on therapeutic or nutritional considerations.

The object of the invention is to provide stable and non-hygroscopic salts of L-carnitine and lower alkanoyl-L-carnitines which are endowed with an enhanced therapeutical and/or nutritional efficacy with respect to their inner salt counterparts.

It should, therefore, be clearly understood that the utility of the salts of the present invention is not confined to their lack of hygroscopicity and higher stability compared to the corresponding inner salts, but also resides in the contribution to the overall therapeutic and/or nutritional value of the salt in its entirety provided by their anionic moiety. This value is, therefore, no longer to be attributed exclusively to the "carnitine" moiety of the salt.

Because of their lack of hygroscopicity these salts can be easily compounded, particularly with a view of preparing solid, orally administrable compositions.

As is well known to experts in pharmacy, the processing of hygroscopic products entails the use of controlled-humidity chambers both for storage and for the processing itself.

Moreover, the finished products must be packed in hermetically sealed blisters in order to avoid unpleasant consequences due to humidity.

All this involves extra costs both for the storage of raw materials and for their processing and packaging.

Among the populations of the industrialised countries there is an increasingly widespread use of food supplements or "nutraceuticals" both by sportsmen (amateurs or professionals) and by people in good health.

The former use L-carnitine or food supplements containing L-carnitine because it facilitates the oxidation of fatty acids and makes a larger amount of energy available to skeletal muscle, thus allowing enhanced performance and giving rise to less accumulation of lactic acid in the athletes' muscles.

People in good health use these food supplements as health foods, i.e. for the purposes of favouring a reduction in serum fat levels and normalisation of the ratio between the various cholesterol fractions in order to prevent diseases related to lipid metabolism disorders.

It has been estimated that the amount of L-carnitine and its derivatives sold for non-ethical purposes is twice that sold for ethical purposes.

The US market for food supplements or nutraceuticals amount to approximately 250 billion dollars, whereas the estimated figure for the European market is approximately 500 billion dollars (Food Labeling News, 1994, "Nutraceuticals" Market said to be a vast one, March, Vol. 2, n° 25; King Communications Group Inc., 1993, "Nutraceuticals" Foods, Drink in Global Market, Food and Drink Daily, April, Vol. 3, n° 503).

Some non-hygroscopic salts of L-carnitine are already known.

For instance EP 0 434 088 (LONZA) filed Dec. 21, 1990 discloses the use of the non-hygroscopic L(-)carnitine L(+)tartrare (2:1) (the preparation and physico-chemical characterization of which were, however, described by D. Muller and E. Strack in Hoppe Seyler's Z. Physiol. Chem 353, 618-622, April 1972) for the preparation of solid forms suitable for oral administration.

This salt presents, however, some drawbacks, such as e.g. the release, after prolonged storage, of traces of trimethylamine which give the product an unpleasant fishy odour. Moreover, L(-)-carnitine L(+)-tartrate (2:1) becomes deliquescent at relative humidity slightly exceeding 60%. Furthermore, L-(+)-tartaric acid is unable to give non-hygroscopic salts with the alkanoyl-L-carnitines, such as e.g. acetyl-L-carnitine.

The aforesaid object of the present invention, i.e. to provide novel, stable and non-hygroscopic pharmacologically acceptable salts of both L-carnitine and lower alkanoyl-L-carnitines wherein the anion moiety contributes to the therapeutic and/or nutritional value of the salt, is achieved by the salts of formula (I): ##STR1## wherein R is hydrogen or a straight or branched lower alkanoyl having 2-5 carbon atoms.

The preferred salts are those wherein R is selected from the group comprising acetyl, propionyl, butyryl, valeryl and isovaleryl.

Since both magnesium and carnitine are eliminated in massive amounts with the sweat and urine during prolonged, intense physical activity, the compounds of the present invention can be used to advantage as food supplements for sportsmen.

Magnesium is an important co-factor of the membrane enzymes involved in muscle contraction.

Disorders of magnesium metabolism are usually associated with a reduction in the total plasma concentration. Abnormally low blood levels of magnesium are associated with cardiovascular, neurological and skeletal muscle disorders deriving from cell contractility and excitability abnormalities.

In physiological conditions, the equilibrium constants of the reactions between Mg²⁺⁺ and ATP favour the formation of an MgATP²⁺ complex which is used as a substrate by many cellular ATPases.

Magnesium also affects the properties of various ion channels, many of which are situated in various excitable cells, and thus performs a regulatory function with regard to the influx of other ions such as sodium, calcium and potassium.

Magnesium exerts a protective action on cardiac function. The involvement of magnesium in influencing cardiovascular function has recently received considerable attention, both as a therapeutic agent to minimise disorders of an electrophysiological nature and as an aetiological factor in diseases such as myocardial decompensation and hypertension. Epidemiological studies have revealed that there is a distinct correlation between the incidence of cardiac ischaemia and the calcium:magnesium ratio in the diet and drinking water. Hypomagnesaemia gives rise to muscle cramps and to increased activity of the autonomic system. EP-A-0 402 755 (LONZA) discloses L-carnitine magnesium citrate as exhibiting slight hygroscopicity and good thermal stability. On page 2, lines 19-20, of this document, it is stated that other magnesium salts of carnitine, such as magnesium aspartate and magnesium orotate show high hygroscopicity.

The following non-limiting examples show the preparation of some non-hygroscopic salts according to the present invention.

EXAMPLE 1 Preparation of L-carnitine magnesium L-(+)-tartrate (ST 1305) ##STR2##

L-carnitine inner salt (0.01 moles), L-(+)-tartaric acid (0.01 moles) and magnesium hydroxide (0.01 moles) were suspended in 15 mL of H₂ O. The resulting mixture was kept under stirring for about one hour till complete solubilization was achieved. The resulting solution was then concentrated under vacuum.

The residue was taken up with acetone and the resulting mixture kept under stirring and then filtered.

A non-hygroscopic solid product was obtained.

Yield: 95%.

DSC (dec.): 180° C.-190° C.

Elementary analysis for C₁₁ H₁₉ NO₉ Mg

    ______________________________________                                                        C %  H %      N %    Mg                                         ______________________________________                                         Calculated (with 7.5% H.sub.2 O):                                                               36.63  6.15     3.88 6.7                                      Found:           36.10  5.84     2.53 6.68                                     ______________________________________                                    

[α]²⁵ _(D) =-4.3(c=1%, H₂ O)

NMR D₂ O δ 4.5-4.6(1H,m,CHOH); 4.35(2H,s,2(CHOH); 3.35-3.45(2H,d,N⁺ CH₂); 3.2((9H,s,(CH₃)₃ N⁺); 2.35-2.45(2H,d,CH₂ COO)

    ______________________________________                                         HPLC                                                                           ______________________________________                                         Column:         μBondapak-NH.sub.2                                          Eluant:         KH.sub.2 PO.sub.4  50 mM-CH.sub.3 CN (35-65)                   Flow-rate:      1 mL/min                                                       pH:             4.7 with H.sub.3 PO.sub.4                                      L-carnitine:    R.sub.t  = 7.6 min                                             L-(+)-tartaric acid:                                                                           R.sub.t  = 11.4 min                                            ______________________________________                                    

EXAMPLE 2 Preparation of acetyl-L-carnitine magnesium L-(+)-tartrate (ST 1105) ##STR3##

Acetyl L-carnitine inner salt (2.03 g; 0.01 moles), L-(+)-tartaric acid (1.5 g; 0.01 moles) and magnesium hydroxide (0.58 g; 0.01 moles) were suspended in 25 mL of H₂ O.

The resulting mixture was kept under stirring for about one hour till complete solubilization was achieved.

The solution was then lyophilized. The residue was taken up with acetone under stirring. By filtration a non-hygroscopic solid product was obtained.

Yield: 95%

Elementary analysis for C₂₃ H₂₁ NO₁₀ Mg

    ______________________________________                                                        C %  H %      N %    Mg                                         ______________________________________                                         Calculated (with 6.4% H.sub.2 O):                                                               38.91  5.99     3.49 6.06                                     Found:           38.27  5.49     3.46 5.90                                     ______________________________________                                    

[α]²⁵ _(D) =+1.8(c=1%, H₂ O)

NMR D₂ O δ 5.6(1H,m,CHOCO); 4.4(2H,s,CHOH--CHOH); 3.8(1H,dd,N⁺ CHH); 3.4(1H,dd,N⁺ -CHH); 3.2(9H,s,(CH₃)₃ N⁺); 2.7-2.5(2H,m,CH₂ COO); 2.1(1H,s,COCH₃)

    ______________________________________                                         HPLC                                                                           ______________________________________                                         Column:         μBondapak-NH.sub.2                                          Eluant:         KH.sub.2 PO.sub.4  50 mM-CH.sub.3 CN (35-65)                   Flow-rate:      1 mL/min                                                       pH:             4.7 with H.sub.3 PO.sub.4                                      Acetyl-L-carnitine:                                                                            R.sub.t  = 6.75 min                                            L-(+)-tartaric acid:                                                                           R.sub.t  = 11.38 min                                           ______________________________________                                    

The compounds of the foregoing examples are non-hygroscopic and highly stable.

The present invention also relates to compositions comprising as active principle(s) at least one of the aforesaid non-hygroscopic pharmacologically acceptable salts and, optionally, one or more pharmacologically acceptable excipients and active ingredients which are well-known to the experts in pharmacy and food technology.

Particularly preferred are the solid, orally administrable compositions such as tablets, chewable tablets and capsules, which comprise a salt of L-carnitine or alkanoyl-L-carnitine of formula (I) in an amount corresponding to 50-2,000, preferably 100-1,000, mg of L-carnitine or alkanoyl-L-carnitine inner salt.

For instance, a composition for preparing tablets is the following:

    ______________________________________                                         Non-hygroscopic L-carnitine salt of formula (I)                                                          500    mg                                            Starch                    20     mg                                            Talc                      10     mg                                            Calcium stearate          1      mg                                                                      531    mg                                            ______________________________________                                    

A composition suitable for preparing capsules is the following:

    ______________________________________                                         Non-hygroscopic L-carnitine salt of formula (I)                                                          500    mg                                            Starch                    20     mg                                            Lactose                   50     mg                                            Talc                      5      mg                                            Calcium stearate          2      mg                                                                      577    mg                                            ______________________________________                                    

The compositions of the present invention may be used as dietary/nutritional supplements for human use or as fodder supplement for veterinary purposes.

Through the synergic action exerted by the component moieties of the present salts, the following results are achieved:

enhanced enzymatic activity bound to the energy metabolism;

improved endurance and adaptation to programs of strenous exercise with achievement of higher performances and shorter rest periods;

strengthening of the functional capacity of the cardiovascular system; and

less tendency to develop muscular cramps. 

What is claimed is:
 1. A salt of L-carnitine or alkanoyl-L-carnitine of formula (I) ##STR4## wherein R is hydrogen or a straight or branched lower alkanoyl having 2-5 carbon atoms.
 2. The salt of claim 1, wherein R is selected from the group comprising acetyl, propionyl, butyryl, valeryl and isovaleryl.
 3. A composition comprising as active ingredient a salt of general formula (I) as defined in claim
 1. 4. The composition of claim 3, further comprising one or more substances selected from pharmacologically acceptable excipients and active ingredients.
 5. The composition of claim 3, in the form of tablets, chewable tablets, capsules, granulates or powders.
 6. The composition of claims 3, in unit dosage form comprising as active ingredient a salt of L-carnitine or alkanoyl-L-carnitine of formula (I), in an amount corresponding to 50-2,000 mg of L-carnitine or alkanoyl-L-carnitine inner salt.
 7. The composition of claim 6, in unit dosage form comprising a salt of L-carnitine or alkanoyl-L-carnitine in an amount of 100 to 1,000 mg of L-carnitine or alkanoyl-L-carnitine inner salt. 